New radio technologies are emerging, and user devices in a communications system are designed to be capable to use multiple radio systems, such as Global System for Mobile communication (GSM), Universal Mobile Telephone System (UMTS) and Personal Communications Services (PCS).
Additionally, new kind of services and other networks than cellular radio systems have also been developed. Examples of such services are Wireless Local Area Network (WLAN) offering a wireless access to the Internet, Global Positioning System (GPS) and Digital Video Broadcasting—Handheld (DVB-H) offering reception of digital television transmissions.
If a communication device supports more than one communications system, such as UMTS, or service protocol, such as DVB-H, the device can be called a multiradio device.
In radio frequency (RF) circuit designs for such multiradio devices, receiver and transmitter chains are usually re-configurable for use in different communications systems. In other words, there are not necessarily separate transceivers for each supported system.
The use of shared resources, such as radio frequency hardware, is a motivation to time domain scheduling of active radio systems. Simultaneous operations also cause inter-system interference, which leads to interoperability problems.
There are several prior art methods to improve the interoperability. One of them is simply using prioritization: a higher priority system can block out a lower priority system. This approach is not practical, since the lower priority system has problems in traffic scheduling.
Another approach is using inter-system handoffs. However, this is not suitable for managing low-level, such as radio frequency hard ware, resources, if inter-system operation has not been solved in the standardization bodies. Namely, during a typical prior-art handoff procedure, one of communication systems requires a resource access independent from the other.